Great Hammerhead Shark

About the Great Hammerhead Shark

The great hammerhead is the largest hammerhead in the world. Adult males are usually around 4 meters long. The biggest specimen ever recorded was 6.1 meters (19.7 ft) long. Great hammerheads are generally solitary, and highly migratory sharks that can be found in tropical and warm-temperate seas. Some populations move seasonally toward cooler waters during the warmer months. They are most commonly found in shallow coastal waters, but they can also occur far offshore at depths up to 300 m (91.4 ft). Their main prey are rays, groupers, and sea catfishes. Their only known predators are killer whales, but other sharks such as the bull shark might hunt young hammerheads.

Biology

The great hammerhead’s distinctive head is useful in finding prey that hides in the sand, particularly rays. On the underside of the head, there are hundreds of small organs called the ampullae of Lorenzini. They help the shark find rays by detecting their electrical signatures. Every living animal gives off an electrical current that sharks can detect in the water. The species has a long life span with individuals reported to live for up to 44 years. Males mature at 2.25–2.69 m (7.4–8.8 ft), while females mature at approximately 2.1–3 m (6.9–9.8 ft).

Great hammerheads are recognizable by their sickle-shaped dorsal fin and their straight head. Other species of hammerhead have a curved head.

Reproduction

Great hammerheads are a viviparous species, meaning mothers give birth to live pups and embryos are nourished through a placenta. Females give birth to between 6 and 42 pups in a single litter after a gestation period of 11 months. Newborn pups are about 50 to 70 cm (19.7–27.6 in) long. Despite giving birth to many pups, only a few survive to adulthood, and once they are mature they only reproduce every two years.

Behaviour

Great hammerheads are specialized hunters of rays. They are known to strike rays from above and to pin them down using their head. They also seem to prefer to immobilize them by biting part of their fins off. Once they’re incapacitated the hammerhead proceeds to eat the rest of their body. Stingray venomous spines are often found inside hammerhead mouths, but they don’t seem to bother the shark.

Conservation

The Great hammerhead is classified as Critically Endangered on the IUCN Red List due to severe population declines caused by overfishing. The species is caught as bycatch, mostly in tuna fisheries, and is also targeted, including in nurseries. Its long fins are highly prized in the shark fin trade and it is also utilized for its meat, leather, and liver oil. Its slow reproduction and long lifespan make population recovery especially difficult.

The species is also listed in CITES Appendix II, which makes it illegal to export them without a permit. Despite these commitments, there are no known international protection initiatives in place for great hammerheads.

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Great Hammerhead Shark Gallery